Oil and gas wells are drilled vertically down into the earth strata with the use of rotary drilling equipment. A tube known as casing is placed down into the well after it is drilled in order to provide stability to the drill hole for and during the subsequent recovery of hydrocarbons from the well. The casing defines the cross-sectional area of the well for transportation of oil and gas upwardly from the well. The casing is usually made of steel and is generally 4.5-8 inches in external diameter and 4-7.5 inches in internal diameter. The casing may hang freely in portions of the well and will often be cemented in place with grout and/or cement. As is well known, after casing a well, the cased well must be perforated through the casing to permit formation fluids to enter the casing from any zones of interest adjacent to the casing.
In addition to simply perforating a well and allowing formation fluids to flow into the well, well production can be improved by subjecting the well and producing formations to fracturing operations in which fractures are induced in the formation using high pressure pumping equipment. Further still, other drilling methods such as horizontal or directional drilling may be employed to enhance hydrocarbon recovery.
However, each of these technologies can be extremely costly such that the cost presents a significant barrier to enhanced production in some applications. Moreover, such techniques may not be able to exploit thin production horizons. Generally, the limitations of these production enhancement technologies results in what the industry refers to as by-passed production.
As a result, there has been a need for systems and methods to effectively enhance production of reservoirs beyond that which may be achieved through simply perforating a well or by the very expensive fracturing or horizontal or directional drilling techniques. In particular, there has been a need for systems and methods that can effectively enhance production and at a cost significantly below that of many past techniques.
More specifically, there has been a need for improved radial or longitudinal drilling in which the well casing can be effectively penetrated in a radial direction to the longitudinal axis of the well to gain access to the surrounding earth strata. Radial access to the formation has been achieved by various techniques including fluid jetting. While fluid jetting is a known technique, there continues to be a need for systems that improve the overall efficiency of such techniques and, in particular, the ability to enable radial jetting by minimizing the number of steps in the overall process of perforating a well and subsequently performing a radial fluid jetting operation.
A review of the prior art reveals that a number of technologies have been utilized in the past. For example, U.S. Pat. No. 6,971,457 describes a method for drilling holes in casing using a multiple U-Joint method. This method allows the jetting tool to be located down well in a different slot than the casing perforator, wherein it can then be used once the perforation is made.
U.S. Pat. No. 6,920,945 also describes a method for drilling holes in casing using a multiple U-Joint method. In this case, once the perforation is drilled, the perforation device is removed and a flexible tube is inserted to penetrate the perforation and jet drill the formation.
Other patents include U.S. Pat. No. 6,550,553 which describes a method for drilling holes in casing using a multiple U-Joint method; U.S. Pat. No. 6,523,624 which describes a method for drilling holes in casing using a flexible spline drive and a cutter to cut holes in casing; U.S. Pat. No. 6,378,629 which describes a method for drilling holes in casing using a multiple U-Joint method; U.S. Pat. No. 6,189,629 which describes a jet cutting tool rotatable in the downhole position allowing for multiple radial drills in which the jet drilling tool erosion drills the casing using a fluid and an abrasive; U.S. Pat. No. 5,853,056 that describes a ball cutter to drill the casing; U.S. Pat. No. 7,441,595 describing an alignment tool to ensure that multiple passage ways can be accessed; and U.S. Pat. No. 7,195,082 describing a directional control system to work with a jet drilling system.
In addition, U.S. Pat. Nos. 6,964,303; 6,889,781; 6,578,636 describe drilling systems for porting a casing and using a jet drilling system for formation drilling.
Further still, U.S. Pat. No. 6,668,948 describes a jet drilling nozzle with a swirling motion applied to the fluid; U.S. Pat. No. 6,530,439 describes a jet drilling hose and nozzle assembly with thruster jets incorporated in the hose to advance the drilling hose during the drilling process; U.S. Pat. No. 6,412,578 describes a multiple U-Joint casing boring technology; U.S. Pat. No. 6,263,984 describes a rotating and non-rotating jet drilling nozzle system; U.S. Pat. Nos. 6,125,949 and 5,413,184 describe a ball cutter for drilling a window in the casing and using a jet drilling assembly for drilling the formation; and, U.S. Pat. No. 4,708,214 describes a jet drilling nozzle assembly.
While the prior art may provide a partial solution, each are limited in various ways as briefly discussed below.
In particular, past systems may be limited by the practical effectiveness of the system downhole or by inherent problems in the design of the systems. Such problems may include the strength, durability and accuracy of a flexible shaft and/or the effectiveness of a ball cutter. Other problems include the number of steps required, the complexity of the systems and, hence the maintenance costs associated with such systems.
Abrasive jet techniques and rotary techniques may be further limited in narrow casing ID's deployments and problems of ports that introduce potential tear/binding points.